1. Field of the Invention
The present invention relates to a technique for diagnosing an electrically operated brake for an automotive vehicle, for any abnormality or defect.
2. Discussion of the Related Art
Published International Application WO97/3869 discloses a method of diagnosing an electrically operated brake which includes an electric motor as a drive source. According to this method, a quantity relating to the output of the electric motor is detected upon operation of the brake, and the electrically operated brake is determined to be abnormal or defective if the detected quantity does not accurately correspond to the magnitude of a drive signal applied to the electric motor.
However, this conventional diagnosing method permits a diagnosis of the electrically operated brake only when the the brake is operated during running of the vehicle. In other words, the conventional method does not permit a diagnosis of the electrically operated brake before running of the vehicle.
When the vehicle is started while it is parked with both a normal brake and a parking brake being applied thereto, it is a common practice to first release the parking brake and then release the normal brake. In this case, there is a time period during which only the normal brake is in operation with the parking brake already placed in the released state. This operation of the normal brake is not for braking the running vehicle. It is desirable to diagnose the electrically operated brake for abnormality, without operation of the brake to brake the running vehicle.